Bone screws and methods of use thereof

ABSTRACT

The invention features bone screws having a threaded screw body and a screw head attached to one end of the screw body, the bone screw further including: a) an interior channel extending longitudinally through the screw head and through at least a portion of the screw body, wherein the interior channel has a width of less than 5.0 millimeters; and b) a plurality of radially-disposed delivery channels connecting the interior channel to the exterior of the screw body, each delivery channel having exterior openings. The invention further features devices that include a bone screw and a delivery manifold detachably attached to the screw head of the bone screw. In addition, the invention features methods of treating a patient having a bone defect by using a bone screw described herein.

FIELD OF THE INVENTION

The invention relates to devices, in particular, bone screws, andmethods of use thereof for the treatment of bone defects.

BACKGROUND OF THE INVENTION

Fixation tools and devices, which are available in a wide variety ofdifferent shapes and sizes, have long been used in the repair of bonedefects, such as bone fractures. A physician typically sets the bone tobe repaired in the proper position and then uses the fixation tools anddevices to secure the bone in that position during the healing process.

A fixation device, such as a bone plate or rod, can be secured to thebone by a fixation tool, such as a bone screw. Alternatively, a bonescrew can be used by itself to repair a bone defect. One drawbackassociated with prior art bone screws is the potential for the bonescrew to back out after implantation. To inhibit back out, bone screwshave been modified with various thread designs and locking features,with some success.

When installing a bone anchor or screw, a surgeon will typically tap ahole, remove the tap and then install the screw into the hole whilemaintaining the alignment of the bone with another bone or prosthesis.The bone screw can be secured in the bony bed by filling the hole beforeinstallation of the screw with a bone cement, such aspolymethylmethacrylate or other fillable and flowable materials.

The use of a solid screw with a bone cement or other fillable materialmay increase the initial stiffness and strength of the repair, but maynot significantly decrease loosening of the screw at the repair site.The substitution of solid screws with cannulated screws that can extrudea bone cement or other fillable material may improve the strength of therepair while at the same time reducing the likelihood that the screwwill loosen and pull out, but distribution of the bone cement orfillable material through the screw and throughout the repair siteremains a problem. Thus, there remains a need for a cannulated bonescrew for use with a bone cement or fillable material that is capable ofsecuring bone at a repair site while also preventing loosening andpull-out of the bone screw following the repair.

SUMMARY OF THE INVENTION

In general, the invention features bone screws, devices incorporatingthe bone screws, and methods of treating a patient having a bone defectby using bone screws as described herein.

Accordingly, in a first aspect, the invention features a bone screw thatincludes a threaded screw body and a screw head attached to one end ofthe screw body; the bone screw further includes a) an interior channelextending longitudinally through the screw head and through at least aportion of the screw body (e.g., through substantially the full lengthof the screw body or through only one-half, one-third, or less of thelength of the screw body), wherein the interior channel has a width ofless than 5.0 millimeters (mm), e.g., less than or equal to about 0.4mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9mm, or 5.0 mm, or wherein the width is in a range spanning any of thepreceding values, e.g., 0.4 to 5.0 mm, 0.5 to 4.0 mm, 0.8 to 3.5 mm, 1.0to 3.2 mm, 1.2 to 2.5 mm, or 1.6 to 2.0 mm; and b) a plurality ofradially-disposed delivery channels connecting the interior channel tothe exterior of the screw body. In several embodiments, the interiorchannel is substantially cylindrical, decreases in width (where theterms “width” and “diameter” are used synonymously in the context of asubstantially cylindrical interior channel) along a direction distal tothe screw head, decreases substantially linearly as a function oflongitudinal distance from the screw head, or has a width that decreasesin step-wise fashion. In another embodiment, the delivery channels ofthe bone screw have exterior openings of varying cross-sectional areas.In another embodiment, the exterior openings are positioned along thelength of the screw body. In an embodiment, the exterior openings arepositioned between the threads of the screw body (e.g., betweenalternating threads of the screw body or each thread of the screw body).In other embodiments, the exterior openings are i) arrayed in increasingcross-sectional area along a direction distal to the screw head, or ii)positioned at substantially equal intervals along at least a portion ofthe screw body, or iii) may be substantially circular, substantiallyslot-shaped, substantially square, substantially polygonal, orcombinations thereof (e.g., the delivery channels may includesubstantially circular and substantially slot-shaped exterior openings).In yet other embodiments, the delivery channels are sized to generatesubstantially equal flow rates of a flowable medium (e.g., a bone voidfiller material, a cement (e.g., polymethacrylate (PMA),polymethylmethacrylate (PMMA), calcium phosphate, or calcium sulfate),or a pharmaceutical agent) extruded through each of the deliverychannels following introduction of the flowable medium through the screwhead into the interior channel. In an embodiment, the cement may be apaste, putty, or slurry. In other embodiments, the cement hardens inless than 2 hours, 1 hour, 30 minutes, 15 minutes, 10 minutes, or 5minutes.

In other embodiments of the bone screw of the first aspect of theinvention, each delivery channel is substantially cylindrical or taperedalong at least a portion of its radial axis. In yet another embodiment,the delivery channels are disposed at more than one angular orientationwith respect to the longitudinal axis of the screw body. In yet otherembodiments, for each of the delivery channels, i) an additionaldelivery channel and exterior opening is positioned at substantially thesame longitudinal distance from the screw head and is positionedsubstantially 180 degrees apart around the longitudinal axis of thescrew body, or ii) two additional delivery channels and exterioropenings are positioned at substantially the same longitudinal distancefrom the screw head and are positioned substantially 120 degrees apartaround the longitudinal axis of the screw body, or iii) three additionaldelivery channels and exterior openings are positioned at substantiallythe same longitudinal distance from the screw head and are positionedsubstantially 90 degrees apart around the longitudinal axis of the screwbody.

In other embodiments of the first aspect of the invention, the bonescrew body further includes at least one exterior groove (e.g., thegroove(s) can be substantially straight or substantially helical)extending along at least a portion of the exterior of the screw body andconnecting at least a subset of the exterior openings of the deliverychannels. In an embodiment, the depth of the exterior groove(s) is lessthan the depth of the delivery channels. In other embodiments, the screwbody further includes a plurality of exterior grooves (e.g., twoexterior grooves on substantially opposite sides of the screw body,three substantially equidistant exterior grooves, or four exteriorgrooves, in which each adjacent pair of the exterior grooves issubstantially equidistant), each extending along at least a portion ofthe exterior of the screw body and connecting at least a subset of theexterior openings of the delivery channels, wherein the depth of each ofthe exterior groove is less than the depth of each said deliverychannel. In other embodiments, the depth of each of the grooves,relative to the major diameter of the bone screw, is between 0.1 mm and1.0 mm. In another embodiment, the plurality of exterior grooves is ofsubstantially identical shape. In other embodiments, the exterioropenings i) range in cross-sectional area from 0.1 mm² to 12 mm² or ii)are substantially circular and range in diameter from 0.1 mm to 4 mm.

In yet other embodiments of the first aspect of the invention, the bonescrew includes between 1 and 200 delivery channels, e.g., 1, 5, 10, 20,30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, or 200, or a rangespanning any of the preceding values. In another embodiment, thedelivery channels are substantially cylindrical. In yet otherembodiments, the length of the screw body is between about 10 mm and 200mm (e.g., between about 20 and 100 mm in length), the major diameter ofthe screw body is between about 0.5 mm and 20 mm (e.g., between about 2and 10 mm in diameter), the threads of the screw body are spaced betweenabout 0.05 mm and 500 mm apart (e.g., between about 0.5 mm to 250 mmapart), the radial height of the threads is between about 0.1 mm and 20mm (e.g., between about 2 and 10 mm), the diameter of the screw head isbetween about 3 mm and 30 mm (e.g., between about 5 and 20 mm), and theheight of the screw head is between about 1 mm and 25 mm (e.g., betweenabout 5 and 15 mm).

With reference to any bone screw dimensions described herein, larger orsmaller bone screws that scale proportionally in some or all dimensionsare also contemplated, as well as larger or smaller bone screws that donot scale proportionally. Generally, the dimensions of a bone screw tobe used in a surgical procedure are selected in accordance with the sizeof the bone or bones being treated.

In yet other embodiments of the first aspect of the invention, the bonescrew is made of a material selected from stainless steel alloy,titanium alloy, commercially pure titanium, cobalt chrome,polyetheretherketone, and calcium phosphate, or combinations thereof. Inaddition, the bone screw may further include a sealable polymericbarrier (e.g., a silicone elastomer, such as a Silastic® brand siliconeelastomer (Dow Corning) or a cross-linked polydimethylsiloxane material)that closes off the driving end of the bone screw from the externalenvironment surrounding the bone screw to form a reserveroir space. Thereservoir space may be filled with a flowable medium that may include,e.g., a pharmaceutical agent, which may distribute evenly along the boneover time. In an embodiment, the sealable polymeric barrier is asilicone elastomer. In another embodiment, the pharmaceutical reservoirhas a volume capacity of between about 0.2 ml and 20 ml.

In yet other embodiments, the screw head is i) machined to fit adelivery manifold capable of introducing a flowable medium to the bonescrew, or ii) machined to fit a rotational driver that is insertedwithin the manifold, or iii) is hollow, or iv) is threaded, or v) ismachined to be driven by a spanner, or vi) includes a hexagonal opening,a Robertson opening, a slotted opening, a Phillips opening, a Torxopening, a triple square opening, a polydrive opening, a one-way clutchopening, a spline drive opening, a double hex opening, or a Bristolopening, or vii) is substantially circular, substantially hexagonal,substantially square, or substantially polygonal.

In yet another embodiment, the bone screw further includes an internalplug that fully or partially occludes the interior channel within thescrew body and that is stationary within, or slidably movable along, theinterior channel. In other embodiments, the plug is positioned at thehollow tip of a fully cannulated screw to prevent escape of flowablemedium from the tip, or it is positioned on, in, or close to the screwhead in order to prevent escape of flowable medium from the screw heador entry of other substances into the screw head and interior channel.The plug can be placed entirely inside the interior channel, or it canscrew into place within the screw head and extend a designated distanceinto the interior channel. The plug can be designed to occlude all, orany subset of, delivery channels (e.g., 1, 2, 5, 10, 20, 30, 50, or moredelivery channels).

In other embodiments, the plug is pre-filled (e.g., prior to insertionof the internal plug into the bone screw, prior to implantation of thebone screw into a patient, or prior to extrusion of a flowable medium(e.g., bone cement) through the internal channel of the bone screw)with, e.g., a flowable medium (e.g., polyethylene, metal alloy, bonevoid filler material, cement, or a pharmaceutical agent) that is capableof releasing by fluid dissolution from the plug.

In a second aspect, the invention features a device that includes thebone screw of the first aspect of the invention and a delivery manifolddetachably attached to the outside of the screw head. In an embodiment,the delivery manifold and the screw head have complementary threadedregions that allow attachment to each other. In another embodiment, thedevice further includes a rotational driver that engages with the screwhead, thereby allowing for rotation of the bone screw about itslongitudinal axis by rotation of the driver. In yet other embodiments,the device is capable of receiving a flowable medium (e.g., a bone voidfiller material, cement, or a pharmaceutical agent) through the deliverymanifold and the bone screw is capable of being tightened, prior tohardening of the flowable medium, by the steps of i) inserting therotational driver through the flowable medium within the deliverymanifold; ii) engaging the screw head with an end of the rotationaldriver; and iii) tightening the bone screw into final position byrotating the rotational driver. In another embodiment, the device iscapable of being tightened by the steps of i) inserting the rotationaldriver through the delivery manifold; ii) engaging the screw head withan end of the rotational driver; and iii) tightening the bone screw intofinal position by rotating the rotational driver. Following removal ofthe rotational driver, a flowable medium is added to the deliverymanifold and injected into the bone screw through the screw head andinto the interior channel by applying pressure at the proximal end ofthe delivery manifold (e.g., by depressing a plunger from the proximalend to the distal end through the delivery manifold towards the screwhead). Alternatively, the bone screw is capable of being tightened by i)inserting the rotational driver through flowable medium already presentwithin the delivery manifold; ii) engaging the screw head with the endof the rotational driver; and iii) tightening the bone screw into finalposition by rotating the rotational driver. In an embodiment, thedelivery manifold includes a Luer lock, e.g., allowing for attachment ofa syringe that can be operated using manual pressure.

In a third aspect, the invention features a device that includes a) abone screw (e.g., a bone screw of the first aspect of the invention)having a threaded screw body and a screw head attached to one end of thescrew body, in which the bone screw further includes: i) an interiorchannel extending longitudinally through the screw head and through atleast a portion of the screw body; and ii) a radially-disposed deliverychannel connecting the interior channel to the exterior of said screwbody; and b) a delivery manifold attached to the screw head, in whichthe delivery manifold is configured to receive a rotational driverwithin the interior of the delivery manifold. An end of the rotationaldriver is configured to engage with the screw head and the screw head ismachined to connect with the rotational driver.

In an embodiment, the delivery manifold is removable and is detachablyattached to the outside of the screw head. In other embodiments, thedelivery manifold is i) connected to the interior of the screw head orii) is connected to the screw head via a butt joint connection (e.g.,using a slidable piece of material to bridge the screw head and deliverymanifold). In another embodiment, the device is capable of receiving aflowable medium (e.g., a bone void filler material, cement, or apharmaceutical agent) through the delivery manifold, and the bone screwis capable of being tightened, prior to hardening of the flowablemedium. For example, the bone screw is capable of being tightened byinserting the rotational driver through the delivery manifold; ii)engaging the screw head with an end of the rotational driver; and iii)tightening the bone screw into final position by rotating the rotationaldriver. Following removal of the rotational driver, a flowable mediummay be added to the delivery manifold and injected into the bone screwthrough the screw head and into the interior channel by applyingpressure at the proximal end of the delivery manifold (e.g., bydepressing a plunger from the proximal end to the distal end through thedelivery manifold towards the screw head).

Alternatively, the bone screw is capable of being tightened by i)inserting the rotational driver through flowable medium already presentwithin the delivery manifold; ii) engaging the screw head with the endof the rotational driver; and iii) tightening the bone screw into finalposition by rotating the rotational driver. In an embodiment, thedelivery manifold includes a Luer lock.

A fourth aspect of the invention features a method of making the bonescrew of the first aspect of the invention. In an embodiment, the bonescrew is made using an extrude hone process that may involve, e.g.,extrusion of adhesive putty under high pressure to provide internalventure, which provides internal edge breaks in the bone screw in areasnot accessible to conventional machining techniques.

A fifth aspect of the invention features a method of treating a patienthaving a bone defect (e.g., subarticular fracture, a defect of the spineor vetebra, or a defect of the radius, ulna, fibula, clavicle, humerus,pelvis, femur, patella, tibia, talus, calcaneus, navicular, cuneiforms,metatarsals, metacarpals, phalanges, scapula, ankle, teeth, or mandible)by a) positioning the bone screw or device of the first, second, orthird aspects of the invention in proximity to the bone defect (e.g.,positioning the bone screw so that it contacts the intraosseous space ofa bone); b) introducing a flowable medium (e.g., a bone void fillermaterial, cement, or a pharmaceutical agent) into the interior channelof the bone screw; c) allowing the flowable medium to be extrudedthrough the delivery channels (e.g., the flowable medium is extrudedthrough substantially all or a plurality of the delivery channels, e.g.,in substantially equal volumes), and d) allowing the flowable medium toharden, thereby fixing the bone screw in place. In an embodiment, themethod involves maxillomandibular or craniofacial fixation, temporaryfixation for repairing a bone defect in a staged reconstruction, glenoidor humeral fixation, patellar fixation, or spine fixation. In otherembodiments, the bone screw is placed within a pedicle, used to anchoran interbody device, used to anchor spinal fusion plates and spacerreplacement, used in an osteoporotic vertebra, or positioned inproximity to the spinous processes of adjacent vertebrae. In yet otherembodiments, the method includes the insertion of a rod, pin, nail, orbone plate in proximity to the bone defect. In another embodiment, themethod involves, prior to step b), fluidically coupling the screw headto a delivery manifold capable of introducing the flowable medium to theinterior channel of the bone screw. In still another embodiment, themethod further includes introducing the flowable medium to the interiorchannel of the bone screw through the delivery manifold. Furthermore,prior to step d), the method further involves i) inserting a rotationaldriver through the flowable medium within said delivery manifold; ii)engaging the screw head with the rotational driver; and iii) tighteningthe bone screw into final position by rotating the rotational driver.

In a sixth aspect, the invention features a kit that includes one ormore bone screws of the first aspect of the invention, the device of thesecond or third aspect of the invention and, optionally, a container offlowable medium, which may be provided in a powder form that may behydrated with a pharmaceutically acceptable fluid (e.g., water, serum,or saline) prior to use, or in a ready to use form (e.g., a paste,putty, or slurry). The kit may further include instructions for use ofthe bone screw, device, or flowable medium to treat a bone defect (e.g.,subarticular fracture, a defect of the spine or vetebra, or a defect ofthe radius, ulna, fibula, clavicle, humerus, pelvis, femur, patella,tibia, talus, calcaneus, navicular, cuneiforms, metatarsals,metacarpals, phalanges, scapula, ankle, teeth, or mandible).

In an embodiment of all aspects of the invention, the bone screw ordevice is sterilized after manufacture, prior to implantation, or priorto inclusion in a kit. In another embodiment of all aspects of theinvention, the flowable medium is provided in a sterile form.

In another embodiment of all aspects of the invention, the bone screwincludes a dual lead (e.g., two threads 180 degress apart winding aroundthe axis of the screw body), which provides for a faster advance of thescrew in the bone. Alternatively, the bone screw can be designed as adual lead, but have one thread omitted, which provides extra spacebetween the thread for delivery channels.

In still another embodiment of all aspects of the invention, the bonescrew includes a screw head, the circumference of which includes aninternal edge break or chamfer on the inside of the radial hole justbeyond the exterior of the screw head. The internal edge break orchamfer allows the flowable medium injected into the interior deliverychannel (or cannula) of the bone screw to flow more easily through thedelivery channel.

In other embodiments of all aspects of the invention, the width ordiameter of the interior channel of the bone screw is substantially thesame along the length of the bone screw. In other embodiments, theinterior channel of the bone screw has more than one width or diameter(e.g., multiple different diameters) along the length of the bone screw.For example, the diameter of the interior channel may increase graduallyalong the length of the bone screw distal from the screw head or maydecrease gradually along the length of the bone screw. In otherembodiments, the interior channel of the bone screw may have severalwidths or diameters that alternate in size from large to small acrossseveral external delivery channels along the length of the bone screw.

In yet another embodiment of all aspects of the invention, the flowablemedium may include a cohesiveness agent, an osteogenic agent, or amedicinal agent. The cohesiveness agent can be selected from the groupconsisting of: a) one or more polymers selected from polysaccharides,nucleic acids, carbohydrates, proteins, polypeptides, poly(α-hydroxyacids), poly(lactones), poly(amino acids), poly(anhydrides),poly(orthoesters), poly(anhydride-co-imides), poly(orthocarbonates),poly(α-hydroxy alkanoates), poly(dioxanones), poly(phosphoesters),poly(L-lactide) (PLLA), poly(D,L-lactide) (PDLLA), polyglycolide (PGA),poly(lactide-co-glycolide (PLGA), poly(L-lactide-co-D, L-lactide),poly(D,L-lactide-co-trimethylene carbonate), polyhydroxybutyrate (PHB),poly(ϵ-caprolactone), poly(δ-valerolactone), poly(γ-butyrolactone),poly(caprolactone), polyacrylic acid, polycarboxylic acid,poly(allylamine hydrochloride), poly(diallyldimethylammonium chloride),poly(ethyleneimine), polypropylene fumarate, polyvinyl alcohol,polyvinylpyrrolidone, polyethylene, polymethylmethacrylate, carbonfibers, poly(ethylene glycol), poly(ethylene oxide), poly(vinylalcohol), poly(vinylpyrrolidone), poly(ethyloxazoline), poly(ethyleneoxide)-co-poly(propylene oxide) block copolymers, poly(ethyleneterephthalate)polyamide, and copolymers thereof; b) a homo- orco-polymer having one or more monomers selected from the groupconsisting of acrolein potassium, (meth)acrylamides, (meth)acrylic acidand salts thereof, (meth)acrylates, acrylonitrile, ethylene, ethyleneglycol, ethyleneimine, ethyleneoxide, styrene sulfonate, vinyl acetate,vinyl alcohol, vinyl chloride, and vinylpyrrolidone); c) a polyphenoliccomplexing agent selected from gallotannins, ellagitannins,taragallotannins, caffetannins, proanthocyanidins, catechin,epicatechin, chlorogenic acid, and arbutin; or d) an agent selected fromalginic acid, arabic gum, guar gum, xantham gum, gelatin, chitin,chitosan, chitosan acetate, chitosan lactate, chondroitin sulfate,N,O-carboxymethyl chitosan, a dextran, fibrin glue, glycerol, hyaluronicacid, sodium hyaluronate, a cellulose, a glucosamine, a proteoglycan, astarch, lactic acid, a pluronic, sodium glycerophosphate, collagen,glycogen, a keratin, silk, and mixtures thereof. The osteogenic agent isselected from the group consisting of transforming growth factors-beta(TGF-β), activins, inhibins, and bone morphogenetic proteins (BMPs). Themedicinal agent is selected from the group consisting of antibiotics,enzyme inhibitors, antihistamines, anti-inflammatory agents, musclerelaxants, anti-spasmodics, analgesics, pro staglandins,anti-depressants, trophic factors, and hormones. In yet otherembodiments of all aspects of the invention, the pharmaceuticallyacceptable fluid is selected from water, saline, a phosphate buffer, abiological fluid, in particular, blood or a fluid that includes bloodcomponents, and glycerol.

In other embodiments of all aspects of the invention, the pharmaceuticalagent of the flowable medium may include, without limitation, anantibody, an antibiotic, a polynucleotide, a polypeptide, a protein(e.g., an osteogenic protein), an anti-cancer agent, a growth factor, avaccine, and demineralized bone matrix. Osteogenic proteins include,without limitation, BMP-2, BMP-3, BMP-3b, BMP-4, BMP-5, BMP-6, BMP-7,BMP-8, BMP-9, BMP-10, BMP-11, BMP-12, BMP-13, BMP-14, BMP-15, BMP-16,BMP-17, and BMP-18. Anti-cancer agents include, without limitation,alkylating agents, platinum agents, antimetabolites, topoisomeraseinhibitors, antitumor antibiotics, antimitotic agents, aromataseinhibitors, thymidylate synthase inhibitors, DNA antagonists,farnesyltransferase inhibitors, pump inhibitors, histoneacetyltransferase inhibitors, metalloproteinase inhibitors,ribonucleoside reductase inhibitors, TNF alpha agonists, TNF alphaantagonists, endothelin A receptor antagonists, retinoic acid receptoragonists, immuno-modulators, hormonal agents, antihormonal agents,photodynamic agents, and tyrosine kinase inhibitors.

DEFINITIONS

As used herein, the term “about” means±10% of the recited value.

By “biocompatible” is meant that the material does not elicit asubstantial detrimental response (e.g., an immune response) in the host.It should be appreciated that a foreign object introduced into a livingbody may induce an immune reaction that will have negative effects onthe host. As used herein, the term “biocompatible” is intended toinclude those materials that may cause some inflammation but does notrise to the level of pathogenesis.

The term “bioresorbable” is meant the ability of a material to beresorbed by the body in vivo. The resorption process involveselimination of the original bioresorbable implant materials through theaction of body fluids, enzymes, or cells. “Strongly bioresorbable” meansthat at least 80% of the total mass of material implanted in vivo isresorbed within one year.

By “bone defect” is meant any bone deficient region, such as a void,gap, recess, or other discontinuity in a bone. A bone defect can beartificially or naturally established, and can occur, for example, dueto disease or trauma. Thus, a bone defect can occur as a consequence ofpathologic or inflammatory diseases, formation and/or removal of a bonetumor, a surgical intervention, a congenital defect, or a bone fracture,and the like. For example, in the case of certain diseases, such as bonetumors, the bone defect may be artificially established due to removalof the tumor tissue. The bone screws of the invention can be applied,for example, in the repair of periodontal defects, in craniofacial ormaxillofacial surgery or reconstruction, in hand surgery, in jointreconstruction, in fracture repair, in orthopedic surgical procedures,and in spinal fusion. The term “bony defect” is also intended to includeanatomical sites where augmentation to a bony feature is desired by thepatient in the absence of disease or trauma, such as in electivecosmetic surgery. Thus, the “defect” can be one that is subjectivelyperceived by the patient, and where augmentation of the bone deficientregion is desired.

By “flowable medium” is meant, generally, a formulation of a resorbableor non-resorbable biocompatible agent, e.g., a polymer, such as athermoset polymer or a thermoplastic polymer, e.g., PMMA(polymethylmethacrylate), a bone void filler material, a cement, or apharmaceutical agent. In particular, the flowable medium may be aresorbable calcium phosphate or calcium sulphate cement, which may allowfor the gradual replacement of the agent with bone. Both resorbable andnon-resorbable biocompatible agents, such as bone cements, have beenused successfully in the treatment of bone defects.

Preferred calcium phosphate bone cements that can be used with the bonescrews of the invention are described in, e.g., U.S. Pat. No. 5,783,217,U.S. Pat. No. 6,027,742, U.S. Pat. No. 6,214,368, U.S. Pat. No.6,287,341, U.S. Pat. No. 6,331,312, U.S. Pat. No. 6,541,037, U.S. Pat.No. 6,953,594, U.S. Pat. No. 6,972,130, U.S. Pat. No. 7,150,879, U.S.Pat. No. 7,318,841, and U.S. Pat. No. 7,517,539, each of which isincorporated herein by reference.

By “bone fill material” or “infill material” is meant any material forinfilling a bone that includes an in-situ hardenable material. The fillmaterial also can include other “fillers,” such as filaments,microspheres, powders, granular elements, flakes, chips, tubules and thelike, autograft or allograft materials, as well as other chemicals,pharmacological agents, or other bioactive agents.

By “major diameter” of a bone screw is meant the diameter of the screwbody, including its threads.

By “osteoplasty” is meant any procedure in which bone fill materialand/or a flowable medium is delivered into the interior of a bone.

By “treating” or “treatment” is meant the medical management of apatient with the intent that an amelioration, repair, or prevention ofan injury or disease, pathological condition, or disorder will result.This term includes active treatment, that is, treatment directedspecifically toward improvement of the injury or disease, pathologicalcondition, or disorder, and also includes causal treatment, that is,treatment directed toward removal of the cause of the injury or disease,pathological condition, or disorder. In addition, this term includespalliative treatment, that is, treatment designed for the relief ofsymptoms rather than the curing of the injury or disease, pathologicalcondition, or disorder; preventive treatment, that is, treatmentdirected to prevention of the injury or disease, pathological condition,or disorder; and supportive treatment, that is, treatment employed tosupplement another specific therapy directed toward the improvement ofthe injury or disease, pathological condition, or disorder.

“Vertebroplasty” includes its ordinary meaning and means any procedurewherein fill material is delivered into the interior of a vertebra.

Other features and advantages of the invention will be apparent from thefollowing detailed description, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of a schematic representation of an embodiment ofa bone screw having straight exterior grooves.

FIG. 1B is a diagonal view of the bone screw of FIG. 1A.

FIGS. 2A and 2B are schematic representations of the bone screw of FIG.1A showing the interior channel and the top face of the screw head.

FIGS. 3A and 3B are sectional views showing the interior of the bonescrew and the tapered delivery channels for enhanced flow.

FIGS. 4A-4C are sectional views showing an internal plug that fully orpartially occludes a portion of the interior channel of the bone screw.

FIG. 4D is a side view of a bone screw showing an internal plug insidethe interior channel of the bone screw.

FIG. 4E is a top view of the bone screw of FIG. 4D.

FIGS. 5A and 5B are side views of an embodiment of a bone screw havinghelical exterior grooves and delivery channels spaced opposite oneanother across the screw body.

FIG. 6 is a diagonal view of an embodiment of a bone screw that lacksexterior grooves.

FIG. 7A is a sectional view of a device that includes a bone screw and aLuer lock delivery manifold coupled via complementary screw threads.

FIGS. 7B and 7C are side views of the device of FIG. 7A with arotational driver inserted into the delivery manifold and engaging thescrew head.

FIG. 7D is a sectional view of the device of FIGS. 7B and 7C.

FIG. 7E is a side view of the device of FIG. 7A showing the flow path offlowable medium through the device.

FIG. 7F is a side view of a device that includes a bone screw, adelivery manifold coupled to the bone screw via complementary screwthreads on one end, and a syringe coupled to the delivery manifold onits other end.

FIGS. 8A and 8B are diagonal views of a Luer lock delivery manifold.

FIG. 8C is a sectional view of the Luer lock delivery manifold of FIGS.8A and 8B.

FIG. 9A is a diagonal view (left) of a spanner having two prongs and adiagonal view (right) of the spanner engaging a screw head withcomplementary holes.

FIG. 9B is a side view of the bone screw shown in FIG. 9A.

FIG. 9C is a diagonal view of a device that includes the bone screw ofFIG. 9B and a Luer lock delivery manifold coupled via complementaryscrew threads, with the spanner of FIG. 9A inserted into the deliverymanifold and engaging the screw head.

FIG. 10A is a side view of a bone screw having equal-sized exterioropenings and an attached delivery manifold in which a flowable medium(e.g., a bone cement) has been injected. The flowable medium is shownbeing extruded through the delivery channels and exterior openings ofthe bone screw. The size of the bubble shown below each exterior openingindicates the volume of the flowable medium being extruded through theexterior opening.

FIG. 10B is a side view of a device that is similar to that shown inFIG. 10A, but in which the bone screw contains exterior openings sizedto achieve a substantially uniform flow rate through each exterioropening. The size of the bubble below each exterior opening indicatesthe volume of the flowable medium being extruded through the exterioropening.

FIG. 11 is a graph showing the relationship of permanent pressure dropto size of obstruction opening in relation to non-cylindrical variationsof delivery channel shape.

FIG. 12A is a side view of a metaphyseal bone screw having a majordiameter of about 4.0 mm and a length of about 35 mm.

FIG. 12B is a side view of a metaphyseal bone screw having a majordiameter of about 4.0 mm and a length of about 25 mm.

FIG. 13A is a side view of a screw-in plug that may be inserted into theinterior channel of a bone screw.

FIG. 13B is a sectional view of the screw-in plug of FIG. 13A.

FIG. 13C is a sectional view of the device of FIG. 7A that includes thescrew-in plug of FIG. 13A.

FIG. 13D is a top view of the device of FIG. 13C.

FIG. 14A is a side view of a bone screw that includes threads anddelivery channels only in the portion of the screw body that is distalto the screw head. In an embodiment, the major diameter of the threadedportion of the bone screw can be 8.0 mm or less, e.g., 6.5 mm. Thelength of the threaded portion of the screw body can be, e.g., 15-30 mm,and the overall screw body length can be, e.g., 25-120 mm. The diameterof the interior channel is, e.g., 1.0-3.0 mm.

FIG. 14B is a close-up side view of the distal portion of the bone screwof FIG. 14A.

FIG. 14C is a close-up side view of the head of the bone screw of FIG.14A.

FIG. 14D is a sectional view of the bone screw of FIG. 14A.

FIGS. 15A, 15B, 15C, and 15D are side views of a bone screw withalternative suture anchors affixed to the screw head.

FIG. 16A is a side view of a bone plate with three bone screws inserted.

FIG. 16B is a sectional view of the bone plate and bone screws of FIG.16A.

FIG. 16C is a side view of a bone plate with one hole occupied by a bonescrew and two holes unoccupied.

FIG. 17A is a side view of a bone screw optimized for anterior cruciateligament reconstruction. In the depicted embodiment, the diameter of thescrew head is substantially the same as the diameter of the screw body,facilitating full insertion of the bone screw, including insertion ofthe screw head. In an embodiment, the length of the screw body can be,e.g., 15-40 mm, the major diameter can be, e.g., 6.0-12.0 mm, and thediameter of the interior channel can be, e.g., 1.0-5.0 mm.

FIG. 17B is a sectional view of the bone screw of FIG. 17A.

FIG. 17C is a diagonal view of the bone screw of FIG. 17A.

FIG. 18A is a side view of a unicortical insertion of a bone screw intoa simulated cross-section of bone.

FIG. 18B is a side view of a bicortical insertion of a bone screw into asimulated cross-section of bone.

FIG. 18C is a side view of the bicortical bone screw insertion depictedin FIG. 18B, with a coupled Luer lock delivery manifold. Arrows show theflow path of flowable medium through the device.

FIG. 19A is a sectional view of a bone screw that does not include a tipplug.

FIG. 19B is a sectional view of the tip of the bone screw of FIG. 19A,with a tip plug inserted.

FIG. 20A is a side view of a bone screw that is optimized for dentalapplications. The bone screw includes an integral cap attached to thehead. The cap can be used to prevent the flow of a flowable medium orbiological material, once extruded through the delivery channels, to aposition beyond the screw head.

FIG. 20B is a sectional view of the bone screw of FIG. 20A.

FIG. 20C is a top view of the bone screw of FIG. 20A.

FIG. 20D is a bottom view of the bone screw of FIG. 20A.

DETAILED DESCRIPTION OF THE INVENTION

The invention features bone screws that allow the passage of a flowablemedium (e.g., a bone cement, such as a resorbable calciumphosphate-based bone cement) through an interior channel of the screwsand extrusion of the flowable medium through a plurality of deliverychannels that lead to exterior openings along the body of the screws.Extrusion of the flowable medium to a position around the exterior ofthe bone screws promotes anchorage of the bone screws in bone afterimplantation and upon hardening of the flowable medium.

In some embodiments, the bone screws are designed to achieve asubstantially uniform rate of flow of the flowable medium throughsubstantially all (or at least a plurality of) the exterior openingsalong the body of the screws and to achieve a substantially uniformdistribution of the flowable medium around the exterior surface of thebone screw, thereby anchoring it in the bone. A substantially uniformflow rate of a flowable medium through the exterior openings of the bonescrew is achieved by, e.g., varying the cross-sectional area of eachsuccessive exterior opening distal to the screw head. In particular, thebone screw can be designed so that each successive exterior openingincreases in cross-sectional area, such that extrusion of the flowablemedium through each exterior opening is substantially the same.

The bone screws of the invention can be used even with bones of reducedquality (e.g., osteoporotic bone) or in revision surgeries (e.g., theycan be used to replaced previously inserted bone screws).

The bone screws of the invention can be used, for example, inosteosynthesis to internally stabilize and/or join bones, e.g.,fractured (broken) bones, either in conjunction with other mechanicaldevices, such as metal plates, pins, rods, or wires, or individually.Without limitation, bone screws include, e.g., small fragment screws,cortex screws, cancellous screws, dynamic hip screws, lag screws,non-self-tapping and self-tapping screws, and malleolar screws. The sizeand function of the bone screw of the invention may vary depending onits intended use (e.g., the bone screw may be fully threaded when usedin the fixation of dense or cortical bone fractures and may be partiallythreaded when used in the fixation of cancellous bone to cortical bone).The head of the bone screw may be modified in order to operate with anyof a number of appropriate drivers and drills known in the art.

The following description of the embodiments of bone screws of theinvention and methods of use thereof are merely exemplary in nature andare in no way intended to limit the invention, its application, or uses.Moreover, while the present invention is described in detail withreference to several different bone screws of the invention, it will beappreciated by those skilled in the art that the present invention isnot limited to the forms and materials specifically described, but mayalso be formed using related forms and other biocompatible materials,e.g., non-resorbable materials, such as titanium, and resorbablematerials, such as allograft, ceramics, and ceramic-polymer mixtures.

There now follows a description of particular embodiments of theinvention.

Structure

Referring to FIGS. 1A, 1B, 2A, and 2B, bone screw 1 includes threadedscrew body 2 and screw head 3 attached to one end of screw body 2. Bonescrew 1 further includes interior channel 4 extending longitudinallythrough screw head 3 and through screw body 2. In addition, bone screw 1includes a plurality of radially-disposed delivery channels 5 connectinginterior channel 4 to the exterior of screw body 2. Delivery channels 5of bone screw 1 have exterior openings 6. The exterior openings 6 thatare closest to screw head 3 have the smallest cross-sectional areas,while exterior openings 6 that are furthest from screw head 3 have thelargest cross-sectional areas. This configuration achieves asubstantially uniform flow rate of a flowable medium through deliverychannels 5. The exterior openings 6 are positioned along the length andbetween threads 7 of screw body 2. Bone screw 1 may also include anoptional interior edge break 50.

Screw head 3 is circular and includes screw head threads 8 on itsexterior, to which a delivery manifold may be attached. Screw head 3additionally contains hexagonal opening 9 internal to screw head 3, inwhich a rotational driver may be inserted. Screw body 2 additionallycontains three straight exterior grooves 10 substantially equally spacedaround screw body 2 and connecting exterior openings 6. In embodiments,bone screw 1 may have one or two external grooves 10 or may have morethan three external grooves 10; the external grooves may be straight,helical, or a combination of the two.

Referring to FIGS. 3A and 3B, a portion of each delivery channel 5 issubstantially cylindrical (although delivery channel 5 can have othershapes, such as a square shape, hexagon shape, diamond shape, etc.),while portion 11 closest to interior channel 4 may be tapered to enhancethe flow characteristics of a flowable medium through delivery channel5. Optional interior edge break 50 is also shown in FIG. 3A.

Referring to FIGS. 4A-4E, internal plug 12 is placed inside interiorchannel 4. Internal plug 12 may fully or partially block passage of aflowable medium distal to internal plug 12 in the direction heading awayfrom screw head 3 as it moves through interior channel 4. Internal plug12 may block a subset of delivery channels 5 and may be affixed withininterior channel 4 or slidably disposed inside interior channel 4,thereby allowing for adjustment of its placement inside interior channel4. Internal plug 12 may be solid, thereby preventing movement offlowable material beyond its position (FIG. 4A), or it may besubstantially porous or hollow (FIGS. 4B and 4C), thereby allowingvarying amounts of flowable material to flow through it to reachdelivery channels 5 distal to the internal plug 12.

An alternative embodiment of a bone screw is shown in FIGS. 5A and 5B.Bone screw 13 of FIGS. 5A and 5B includes two helical exterior grooves14 equally spaced around screw body 15. Each delivery channel 16 andexterior opening 17 is spaced directly opposite a second deliverychannel 16 and exterior opening 17 across screw body 15.

Referring to FIG. 6, bone screw 18 does not include exterior grooves.

Operation

Referring to FIGS. 7A and 8A-C, delivery manifold 19 in the form of,e.g., a Luer lock, is attached to to screw head 3 of bone screw 1, whichhas been positioned in proximity to a bone defect in the course of,e.g., a surgical procedure. Delivery manifold 19 includes threaded end20 that is complementary to screw head threads 8 (as shown in FIG. 7B)of bone screw 1.

Referring to FIGS. 7B-D, following attachment of delivery manifold 19,rotational driver 22 having, e.g., hexagonal end 23, as shown, oranother driver shape, such as a Robertson driver, a slotted driver, aPhillips driver, a Torx driver, a triple square driver, a polydrivedriver, a one-way clutch driver, a spline drive driver, a double hexdriver, or a Bristol driver, is then inserted into delivery manifold 19,and hexagonal end 23 can engage hexagonal opening 9 (as shown in FIG.7A) of screw head 3. Rotational driver 22 may be rotated clockwise orcounterclockise (depending upon thread direction) to tighten bone screw1 into final or near-final position. Alternatively, bone screw 1 may bepositioned into final or near-final position using a rotational driverin the absence of delivery manifold 19.

Rotational driver 22 is then removed and a flowable medium (e.g., a bonecement) may be introduced through proximal end 21 of delivery manifold19 by, e.g., a syringe or other injection device. Alternatively,delivery manifold 19 may be removed from bone screw 1, filled with theflowable medium, and reattached to bone screw 1. The flowable medium maybe introduced into bone screw 1 through delivery manifold 19 using,e.g., a syringe plunger moving through delivery manifold 19 in thedirection from proximal end 21 to threaded end 20. The flowable mediumis injected into bone screw 1 and its interior channel 4, and the cementis extruded substantially uniformly through delivery channels 5 andexterior openings 6. The flowable medium forms a substantially uniformcoat around bone screw 1.

Following injection of the flowable medium, bone screw 1 is furthertightened, if necessary, using rotational driver 22, which may beinserted through delivery manifold 19 or may be used after deliverymanifold 19 is detached. After tightening of bone screw 1, deliverymanifold, 19 is detached (if not already removed) and hexagonal opening9 of screw head 3 may be sealed, e.g., using a sealable polymericbarrier, such as a silicone elastomer (e.g., Silastic®, Dow CorningCorporation, Midland, Mich.), or other means, such as a plug that may besecured by screwing onto the screw head.

Referring to FIGS. 9A-9C, in an alternative embodiment, rotationaldriver 24 is a spanner having two prongs 25 (FIG. 9A), and screw head 26includes complementary holes 27 (FIG. 9B) to engage rotational driver 24(FIG. 9C).

The bone screws of the present invention provide numerous advantagesover other bone screws known in the art. For example, in someembodiments of the bone screws of the present invention, the diameter ofthe interior channel is smaller than in cannulated bone screws in theart, resulting in improved strength and the option of reduced overallscrew size. In addition, by having a smaller interior channel diameter,bone screws of the present invention are optimized for use withstate-of-the-art bone cements, e.g., fourth-generation calciumphosphate-based bone cements, which have reduced viscosity and thusrequire application of less pressure than older bone cements. Inadditional embodiments, the threaded screw head allows for airtightattachment of a removable delivery manifold, e.g., a plastic manifold,which, in turn, facilitates loading of flowable medium by allowing asurgeon or other user to apply manual pressure rather than hydraulicpressure. This reduces the likelihood of unwanted introduction of airembolisms into the bone cavity or other surgical site. In addition,unlike prior art screws that require connection of a delivery manifoldinside the rotational driver, producing very small orifices andcorrespondingly high operating pressure, bone screws of the presentinvention have no restriction in the flow path of the flowable medium,reducing the necessary operating pressure.

Furthermore, in some embodiments, e.g., screws designed for use inanterior cruciate ligament reconstruction, the diameter of the screwhead is substantially the same as the diameter of the screw body,allowing for total implantation of the screw head within the bone, asthe screw may be driven by a rotational driver inserted inside the screwhead.

It is also significantly easier to remove, or adjust the position of, abone screw of the present invention that has been placed in a surgicalsite, in comparison to bone screws of the art. Because the rotationaldriver is inserted inside the screw head, it is not necessary to graspthe external surface of the screw head in order to remove an implantedscrew prior to hardening of the cement.

Upon hardening of the cement around a bone screw of the presentinvention, the bone screw is more stable and secure than a conventionalscrew because of the even distribution of cement that covers a largepercentage of the surface area of the screw body and contacted bone.This increased stability reduces the likelihood of “backout” of a screwfrom the surgical site, which may occur with a conventional screw.

In additional embodiments, the presence of exterior grooves facilitatesequalized distribution of flowable medium along the exterior surface ofthe screw. For example, if one exterior opening is blocked, flowablemedium from an adjacent exterior opening may flow along an exteriorgroove to “back-fill” or compensate for the blocked opening. Thepresence of exterior grooves, in particular, straight exterior grooves,can also increase the strength characteristics of the screw body.

In additional embodiments, use of an adjustable interior plug allows forselective delivery of flowable medium to desired delivery channels whileblocking off other delivery channels. Such a plug may be designed to bepushed in or screwed in and may be either permanent or removable. Inaddition, in some embodiments, the tip or distal end of the screw body,i.e., the end of the screw body distal to the screw head, may bemanufactured to be open or closed; in open embodiments, a removable tipplug may be added as needed according to the surgical indication. Theinclusion of such adjustable plugs significantly increases theflexibility of use of bone screws of the present invention.

EXAMPLES

The following examples are to illustrate the invention. They are notmeant to limit the invention in any way.

Example 1: Use of a Bone Screw of the Invention to Repair a Fracture orOther Bone Defect

A bone screw of the invention can be used to provide fracture support,e.g., for a subarticular fracture, in conjunction with conventionalfixation. The site to be supported can be accessed using either apercutaneous or open technique. The extraction technique preferablyensures maximal bone conservation.

Uni-Cortical and Bi-Cortical Fixation

A bone screw of the invention can be used for uni-cortical fixation tocross one of the sections of the thick cortical wall of a bone, as shownschematically in FIG. 18A. An exemplary bone screw for uni-corticalfixation is, e.g., 25-55 mm long, with, e.g., a 4.0 mm major diameterand, e.g., a 1.6 mm interior channel diameter.

Alternatively, for bi-cortical fixation, the bone screw penetrates allthe way through the bone and reaches the opposite thick cortical wall,as shown schematically in FIG. 18B. An exemplary bone screw forbi-cortical fixation is, e.g., 60-80 mm long, with, e.g., a 4.0 mm majordiameter and, e.g., a 1.6 mm interior channel diameter.

In each instance, the exterior openings are located in the interior ofthe bone, where unsupported fragment sections may be held by cementinjected therein. The bone screw includes a threaded head to which adelivery manifold, e.g., a disposable adaptor compatible with adisposable syringe, is directly attached to form an airtight seal. Forexample, a delivery manifold can be made of plastic and include a Luerfitting on one end for connection with syringes, and threading on theother end for connection to the screw head. To facilitate the surgery,the delivery manifold can be attached to the bone screw on the surgicaltable prior to insertion into the patient, rather than having to wait toconnect the delivery manifold once the screw is in the bone, where itcan become difficult to locate, align, and connect. In order to placethe bone screw in position, a rotational driver is inserted through thedelivery manifold, as shown in FIG. 7B, and engaged with the screw head.

When the screw is positioned appropriately, the rotational driver isremoved, and a conventional syringe is attached. The syringe can beprepackaged to include an appropriate flowable medium, e.g., calciumphosphate bone cement, a saline solution used to irrigate the site priorto introduction of cement, an antibiotic, or a fibrinolytic agent usedto prevent or disrupt clot formation; alternatively, the flowable mediumcan be introduced into an empty syringe. Upon attachment of the syringe,manual or “finger” pressure is then applied to the syringe to inject theflowable medium into the surgical site, e.g., the bone interior. Thelarge total area of the exterior openings in relation to thecross-sectional area of the interior channel allows the surgeon or otheruser to apply only light pressure, which in turn minimizes the forcesgenerated by advancing flowable medium and additionally minimizes therisk of tissue damage or air embolism. If surgically indicated, anyflowable medium or other liquid at the surgical site can be withdrawn bypulling back on the syringe. The introduction and withdrawal of flowablemedium or other liquid can be repeated as appropriate, using the same ora different syringe each time. In this manner, it is possible, forexample, to irrigate thoroughly, apply an antibiotic or otherappropriate biological agent, and then apply bone cement, all withoutneeding to move the screw in or out of the surgical site.

A depiction of the flow path of the injected cement is shown in FIG.18C.

Prevention of Terminal Extrusion

In some instances, it is undesirable to permit terminal extrusion ofbone cement or other flowable medium from the tip of the screw distal tothe screw head. Accordingly, in one embodiment, a bone screw is notfully cannulated, i.e., the interior channel does not extend all the waythrough the tip. In some surgical contexts, however, e.g., osteoporotichip fracture, it is desirable to use a fully cannulated screw, e.g., inorder to allow for the use of a guide wire to place the screw prior tofilling and extrusion of flowable medium. In such instances, followingplacement of the bone screw in the surgical site, a solid internal plugis pushed through the interior channel to the tip. The bone screw isdesigned to have a narrowed tip so that the plug wedges into place andis not released from the screw. Following insertion of the plug, bonecement or other flowable medium is loaded into the screw, and theflowable medium is extruded through the delivery channels but notthrough the tip. Having the ability to plug the tip of a fullycannulated bone screw significantly increases safety and flexibility ofuse, e.g., in situations in which injection of bone cement into softtissue outside the bone, e.g., a joint, would be problematic or evencatastrophic.

Example 2: Use of a Bone Screw of the Invention to Facilitate DentalImplant

A blind hole created during tooth replacement often requires a bonegraft in order to provide support for the post of a dental implant. Abone screw of the invention can be used to facilitate placement of suchan implant. As shown in FIGS. 20A-20D, a bone screw optimized for dentalapplications contains a curved cap affixed to the screw head. Forexample, the bone screw can have an interior channel diameter of 1.0-2.0mm, e.g., 1.2 mm, and a major diameter of 3.0-5.0 mm, e.g., 3.0 mm.

The bone screw is first inserted into, e.g., the maxilla or mandible,and bone cement or other flowable medium is injected and evenlydistributed along the axis of the hole. The curved cap is shaped tocontain the flowable medium. The cement can act to rebuild the lost bonestock, which allows for increased height of bone anchorage and permitssufficient stability for subsequent insertion of a dental implant overthe bone screw.

In an alternative dental implant procedure, a bone screw of theinvention can be inserted into a hole in the maxilla or mandible as atemporary measure, allowing new bone to grow in. Once bone growth hasoccurred, the bone screw is removed, and a conventional dental implantis inserted into the augmented bone site.

Example 3: Use of a Bone Screw of the Invention to Repair Fractures NearJoints that are Reconstructed but do not have Enough Load-BearingStrength with Conventional Fixation Alone

A patient presents with a fracture of the tibia or femur occurring nearthe tibial-femoral or tibial-talar joint. For example, in a high-speedautomobile collision, the femur just above the knee can break when thecrash victim's bent leg hits the dashboard. The bone may break into two,three, or more pieces. The site to be repaired can be accessed using apercutaneous or open technique. The small profile of cement connectionmeans the screw and cement can be done with a wide incision (open) orwith a very small incision (closed).

By using a bone screw of the invention, subsequent screw removal ispossible while ensuring maximal bone conservation. For example, a screwdesigned for use with an interior rotational driver, e.g., an internalhex driver, eliminates the need to use a large external driver, e.g., awrench. Because healing bone grows up and around the head of a screwthat has been inserted into a surgical site, insertion of a large toolis difficult and would result in significant bone loss or damage toadjacent bone. Integration of the interior channel and screw headrotational driver opening allows use of a small drill or pick to removea small amount of bone directly over the screw head and insertion of arotational driver to pull out the screw with minimal effect on adjacentbone.

Alternatively, in an embodiment in which the screw head is notsignificantly larger than the screw body, a cannulated chamfer can bedrilled over the screw, and the friction generated thereby allowsextraction of the screw with minimal bone loss. In this configuration,for screws having spiral exterior grooves, the torque necessary toextract the screw prior to setting of the bone cement is reducedsignificantly (e.g., by 10%, 20%, 30%, 33%, 40%, 50%, or more, e.g.,from about 3 Newton meters to about 2 Newton meters) relative to priorart screws. In contrast, after setting of the bone cement, the forceneeded to extract the bone screw of the invention is significantlyincreased relative to prior art screws (e.g., by a factor of 1.1, 1.2,1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.5, or even 10.0, e.g., from about300 Newtons to about 1,600-1,800 Newtons).

Example 4: Use of a Bone Screw of the Invention to Repair aContralateral Defect

Where a contralateral defect is present, e.g., in metaphyseal bone, abone screw of the invention can be inserted opposite the defect, so thatthe screw tip is positioned close to the defect. Next, flowable mediumis injected at the site of the defect. By inserting the bone screwopposite the defect rather than through it, damage to the blood supplyon the defect side of the bone is avoided, and a second incision forgrafting cement or other biological material is not needed.

Example 5: Use of a Bone Screw of the Invention in Conjunction withOther Internal Fixation Devices

Bone screws of the invention can be used in conjunction with otherinternal fixation devices such as plates, including locking plates, andnails. The screw is constructed so that it can be inserted through oneor more of the existing holes in the plate or nail without weakening theplate or nail construct. This technique is particularly useful in thecontexts of bone comminution or osteoporotic bone, where the structureof the bone may be too fragile to allow a conventional screw to obtainstable purchase in the weakened bone site or successfully fasten theplate or nail to the weakened bone site, and if the hole in the plate ornail were left empty, it would result in a stress riser in the plate ornail. In such an instance, a bone screw of the invention is insertedinto the hole, bone cement is injected and distributed uniformly aroundthe axis of the screw, and the bone cement is allowed to harden, fixingthe plate or nail to the bone.

For example, FIGS. 16A-16C depict bone screws of the invention insertedinto a bone plate designed to receive three locking screws. Bone screwsof the invention can be used in all three holes, or can be used for onlyone or two of the holes, depending on the surgical procedure and thequality of the bone site.

In some instances, bone screws of the invention can be used in revisionsurgeries, in which prior art screws or plates exhibit loosening orweakening over time. Replacing a prior art screw with a screw of thepresent invention can provide greater stability and reinforcement.

Example 6: Use of a Bone Screw of the Invention in Conjunction withReattachment of Ligaments or Tendons

In situations requiring reattachment of ligaments or tendons, there is arisk that sutures may pull out of the attaching bone. Suture anchors,e.g., washer-type devices, are known in the art, but such anchors mayalso be displaced if the bone quality is inadequate. A suture anchor canbe attached to a bone screw of the present invention, as shown, e.g., inFIGS. 15A-15D, and the bone screw can be firmly cemented into a bonesite that might otherwise be too weak or comminuted to secure aconventional bone screw.

Example 7: Use of a Bone Screw of the Invention for Anterior CruciateLigament (ACL) Reconstruction

Bone screws of the present invention can be used to position and anchorreplacement of the ACL following a tear. A hole is drilled in the boneat each end, and a graft is placed where the ACL should be. The graft isgenerally longer than the ACL. The screws can be used to hold the graftto the bone. In bone screws of the invention for which the diameter ofthe screw head is substantially the same as the diameter of the screwbody, e.g., the bone screws depicted in FIGS. 17A-17C, the screw headcan readily be sunk within the graft and/or bone by using a rotationaldriver inserted inside the screw head, thereby facilitating the ACLreconstruction.

All publications, patents, and patent applications mentioned in theabove specification are hereby incorporated by reference. Variousmodifications and variations of the described method and system of theinvention will be apparent to those skilled in the art without departingfrom the scope and spirit of the invention. Although the invention hasbeen described in connection with specific embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention that are obvious to thoseskilled in the art are intended to be within the scope of the invention.

Other embodiments are in the claims.

What is claimed is:
 1. A device comprising: a bone screw including: ascrew body including a plurality of external threads extending along atleast a portion of the screw body; a screw head attached to one end ofthe screw body; an interior channel extending longitudinally through thescrew head and through at least a portion of the screw body, wherein theinterior channel has a width of 5.0 millimeters (mm) or less; aplurality of radially-disposed delivery through channels connecting theinterior channel to an exterior of the screw body, the delivery channelscomprising exterior openings; a screw tip attached to an end of thescrew body opposite to the screw head, wherein the screw tip is narrowerthan the screw body; and at least one helical exterior groove extendingthrough and interrupting more than one of the plurality of threads alongat least a portion of the exterior of the screw body and partially intothe narrower screw tip and wherein the at least one helical exteriorgroove includes all the exterior openings of the plurality of theradially-disposed delivery channels therein; and a delivery manifolddetachably attached to an outside of the screw head.
 2. The device ofclaim 1, wherein the interior channel has a width of up to 2.0 mm. 3.The device of claim 1, wherein the exterior openings are: of varyingcross-sectional areas; positioned along the length of the screw body;positioned between one or more of the threads of the screw body; arrayedin increasing cross-sectional area along a direction distal to the screwhead; substantially circular, substantially cylindrical, substantiallyslot-shaped, substantially square, or substantially polygonal; orcomprised of substantially circular exterior openings and substantiallyslot-shaped exterior openings.
 4. The device of claim 1, wherein thedelivery channels are sized to generate substantially equal flow ratesof a flowable medium extruded through each delivery channel followingintroduction of the flowable medium through the screw head into theinterior channel.
 5. The device of claim 1, wherein the depth of the atleast one helical exterior groove is less than the depth of the deliverychannels.
 6. The device of claim 1, wherein: the length of the screwbody is between 10 mm and 200 mm; the major diameter of the screw bodyis between 2 mm and 20 mm; the threads of the bone screw are spacedbetween 0.5 mm and 500 mm apart; the radial height of the threads isbetween 0.1 mm and 20 mm; the diameter of the screw head is between 3 mmand 30 mm; or the height of the screw head is between 1 mm and 25 mm. 7.The device of claim 1, wherein the bone screw comprises stainless steelalloy, titanium alloy, commercially pure titanium, cobalt chrome, orpolyetheretherketone.
 8. A device comprising: a bone screw comprising anexternally threaded screw body and a screw head attached to one end ofthe screw body, the bone screw further comprising: an interior channelextending longitudinally through the screw head and through at least aportion of the screw body, wherein the interior channel has a width of5.0 millimeters (mm) or less; a plurality of radially-disposed deliverythrough channels connecting the interior channel to an exterior of thescrew body, the delivery channels comprising exterior openings; a screwtip attached to an end of the screw body opposite to the screw head,wherein the screw tip is narrower than the screw body; and at least onehelical exterior groove extending through and interrupting a pluralityof the external threads of the screw body along at least a portion ofthe exterior of the screw body and partially into the narrower screw tipand wherein the at least one helical exterior groove includes all theexterior openings of the radially-disposed delivery channels therein;and a delivery manifold attached to the screw head, wherein the deliverymanifold is configured to receive a rotational driver within an interiorof the delivery manifold, wherein an end of the rotational driver isconfigured to engage with the screw head and wherein the screw head ismachined to fit the rotational driver.
 9. The device of claim 8, whereinthe delivery manifold is removable and is detachably attached to anoutside of the screw head.
 10. The device of claim 8, wherein thedelivery manifold is connected to the interior of the screw head. 11.The device of claim 8, wherein the delivery manifold is connected to thescrew head via a butt joint connection.
 12. The device of claim 8,wherein the screw head further includes a sealable polymeric barrierthat separates an interior region of the screw head from the exteriorenvironment of the bone screw, thereby forming a reservoir within thescrew head.
 13. The device of claim 12, wherein the sealable polymericbarrier is a silicone elastomer.
 14. The device of claim 8, furthercomprising an internal plug that fully or partially occludes theinterior channel or the delivery channel, wherein the internal plug ispositionable along the length of the interior channel or is a solidstate component of the bone screw.
 15. The device of claim 8, whereinthe bone screw is capable of delivering bone cement through each of thedelivery channels following introduction of the bone cement through thescrew head into the interior channel.
 16. The device of claim 8, whereinthe interior channel is substantially cylindrical.
 17. The device ofclaim 8, wherein the screw head includes at least one exterior thread.18. The device of claim 17, wherein the delivery manifold includes atleast one interior thread adapted to engage with the at least oneexterior thread of the screw head.
 19. The device of claim 8, whereinthe depth of the at least one helical exterior groove is less than thedepth of the delivery channel.